Problem in mesh due to boolean modifier
In your case using a boolean to dig this slot seems like the thing to do. Maybe first simplify your topology, i.e. delete one edge loop out of 2 like this (ring select edge loops, then checker deselect, then select edge loops then dissolve edge loops):

Once you apply the Boolean modifier you have this shape:

You need to work on it to have a clean topology and a sharp angle, begin by creating a bevel along the slope:

You must end up with something like this, a topology with quads only:

Here is what it gives with a Subdivision Surface modifier: